Visual/Physical Check

VISUAL/PHYSICAL INSPECTION

Important
^ The importance of this step cannot be stressed too strongly - it can lead to correcting a problem without further checks and can save valuable time.
One of the most important checks that must be done as part of any diagnostic procedure is a careful visual/physical inspection. This can often lead to correcting a problem without further steps. Inspect all transmission control wires for correct and good connections, burned or chafed spots, pinched wires, or contact with sharp edges or hot exhaust pipes. The visual/physical inspection is important and must be done carefully and thoroughly.


Basic Knowledge Required
You should understand the basic theory of electricity. This will include the meaning of voltage, amps, ohms, and what happens in a circuit with an open or a shorted wire. You should also be able to read and understand wiring diagrams. This will help you to follow diagnostic procedures.
A short to ground will be referred to as a ground so that it can be distinguished from a short between wires.

Note: Lack of basic knowledge of this powertrain when performing diagnostic procedures could result in incorrect diagnostic performance or damage to powertrain components. Do not, under any circumstances, attempt to diagnose a powertrain problem without this basic knowledge.


Special Tools
You should be able to use a break out box, a Digital Volt Ohm Meter (DVOM), a circuit tester, jumper wires or leads and a line pressure gage set. The functional test procedures are designed to verify the correct operation of electronic components in the transmission. This will eliminate the unnecessary removal of transmission components.

Tech 1/Scan Tool
The diagnostic procedures in this manual assume the use of a scan tool. The Tech 1 is able to perform functions, such as, bi-directional communication that other scan tools are unable to perform, it has been made an essential tool. The term scan tool will continue to be used for simplicity's sake. Any procedure calling for bi-directional communication with the PCM will require the use of a Tech 1. Instructions on connecting and using the various Tech I functions are contained in the Tech 1 owner's manual.

Note: If a wire is probed with a sharp instrument and is not properly sealed afterward, the wire will corrode and an open circuit will result.
Diagnostic test probes are now available that allow you to probe individual wires without leaving the wire open to the environment. These probe devices are inexpensive and easy to install, and they permanently seal the wire from corrosion.

HOW TO USE THIS SECTION
When diagnosing any condition on the HYDRA-MATIC 4L60-E, begin with the "Functional Test Procedure" in this section. After the cause of a condition is determined, refer to "Service and Repair" for repair procedures.

Diagnosis
The PCM is equipped with a self diagnostic feature that detects system failures and aids the technician in locating a faulty circuit. The PCM has a memory for comparing the various input information to set information. These conditions are described in each diagnostic trouble code chart. If a reading is not what the PCM is programmed to accept, it will store a DTC and go into default actions or values.
In addition, a diagnostic circuit check is provided to verify that the PCM is able to store and display DTC(s). When the "diagnostic" terminal of the DLC is grounded, with the ignition switch "ON," engine "OFF," DTC 12 should flash. The PCM is actually monitoring the distributor reference circuit on gasoline engines or the engine speed sensor circuit on diesel engines. Both circuits should be at 0 volts with the engine not operating. If DTC 12 will not flash, refer to CHART A-1 or CHART A-2 for diagnosis information.


Important
^ Always check for DTC 12 before proceeding to diagnose any other DTC(s). The presence of DTC 12 is an indication that the PCM is able to perform the diagnostic function.

An "Intermittent" diagnostic trouble code is one which does not reset, and is not present while working on the vehicle. This is often caused by a poor connection. The diagnostic trouble code chart will contain "Diagnostic Aids" to help find intermittents.

A "hard" diagnostic trouble DTC is one that will reset, because the condition causing the DTC is still present while working on the vehicle. The diagnostic trouble code chart will lead to the cause of the problem.

An abnormal voltage reading, when the problem occurs, indicates the problem may be in that circuit. If the wiring and connectors check OK, and a Diagnostic Trouble Code (DTC) was stored for a circuit having a sensor, substitute a known good sensor and recheck.

^ Loss of diagnostic trouble code memory: To check, disconnect the TP sensor and idle engine for about 15 seconds. DTC 22 should store, and kept in memory when ignition is turned "OFF," for at least 10 seconds. If not, check for open in CKT 440 to the PCM.

^ Check:
- Electrical system interference caused by a defective relay, PCM driven solenoid or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.
- Improper installation of electrical options, such as light, 2-way radio, etc.
- Ignition secondary shorted to ground.
- CKT 419 (MIL) and CKT 451 (diagnostic test) intermittently shorted to ground.
- PCM power and grounds for location.
- Incorrect or defective PROM.

Note: If CKT 440 has 12 volts to the PCM at all times, replace the PCM.